A senior U.S. official told TIME that the Commission has uncovered evidence suggesting that between eight and ten of the 14 "muscle" hijackers—that is, those involved in gaining control of the four 9/11 aircraft and subduing the crew and passengers—passed through Iran in the period from October 2000 to February 2001. Sources also tell TIME that Commission investigators found that Iran had a history of allowing al-Qaeda members to enter and exit Iran across the Afghan border. This practice dated back to October 2000, with Iranian officials issuing specific instructions to their border guards—in some cases not to put stamps in the passports of al-Qaeda personnel—and otherwise not harass them and to facilitate their travel across the frontier.

The caveats begin right away.

For example, the report apparently describes the Iranian cooperation with al Qaeda as "permissive" rather than active. I suspect that is similar to what pre-9/11 Pakistan was doing.

Next, the story notes that the 9/11 Commission "report does not, however, offer evidence that Iran was aware of the plans for the 9/11 attacks." And while Iran may even have offered to work with bin Laden in the past, that offer was declined by the terrorist leader "because he did not want to alienate his supporters in Saudi Arabia." The report apparently does not offer firm evidence that Iran participated in the 1996 Khobar Towers bombing, as is often alleged.

One final tidbit about the 9/11 commission. It has an interesting PR strategy:

The release of the report Thursday will be followed by a somewhat unusual outreach campaign. Commission members plan to split up into bipartisan pairs and travel the country discussing their findings and urging adoption of their recommended reforms.

Commissioners, who were criticized for appearing too partisan during public hearings earlier this year, also have agreed to avoid campaign appearances and other political activities that might undermine the credibility of their work, officials said.